This disclosure relates to a delivery device, methods of manufacture thereof and to articles comprising the same. In particular, this disclosure relates to a high output, high capacity delivery device for delivering liquid precursor compounds in the vapor phase to reactors.
Semiconductors comprising Group III-V compounds are used in the production of many electronic and optoelectronic devices such as lasers, light emitting diodes (LEDs), photodetectors, and the like. These devices comprise different monocrystalline layers with varying compositions and with thicknesses ranging from fractions of a micrometer to a few micrometers. Chemical vapor deposition (CVD) methods using organometallic compounds are generally employed for the deposition of metal thin-films or semiconductor thin-films, such as films of Group III-V compounds. Such organometallic compounds may be either liquid or solid.
In CVD methods, a reactive gas stream is generally delivered to a reactor to deposit the desired film for electronic and optoelectronic devices. The reactive gas stream is either a neat gas or is composed of a carrier gas, such as hydrogen, saturated with precursor compound vapor. When the precursor compound is a liquid, a reactive gas stream is obtained by passing (i.e. bubbling) a carrier gas through the liquid precursor compound in a delivery device (i.e. a bubbler).
FIG. 1 depicts a commonly used method of transporting precursor vapors from a delivery device 100 to a reactor (not shown). A dip tube 103 connected to the inlet 102 is used to transport the carrier gases into the liquid precursor 106, while an outlet 104 is used to transport the carrier gas along with the precursor vapors to the reactor. The flow of the carrier gas through a simple butt-ended dip tube 103 produces buffeting at the end of the dip tube 200 (sometimes referred to as an injector). The buffeting produces splash back of the precursor into the dip tube causing a constant wetting of the inner dip tube surface near the end of the dip tube. Many precursors are oxygen and moisture sensitive and tend to form a solid reactive product 108 when exposed to the residual moisture and oxygen present in even the highest purity carrier gas. During use, the reactive product 108 builds up on the inside of the dip tube 103. For example, when the liquid contained in the delivery device 100 is trimethyl gallium, a solid crust of gallium hydroxide/gallium oxide reaction product 108 is produced on the inner surface of the dip tube 103. As the amount of the reactive product 108 deposited on the inner surface grows larger, it constricts the flow path of the carrier gas and eventually impedes the flow of the carrier gas through the delivery device 100. This is particularly a concern in permanently installed delivery devices that are continuously fed from a reservoir as described in U.S. Pat. No. 8,555,809 to Woelk et al.
EP0210476A1 to Markowicz attempts to prevent the formation of large bubbles and favor the formation of small bubbles by redesigning the bottom of the dip tube. It teaches that the dip tube may be suitably machined at its lower end to provide a plurality of openings, for example, cut up into the sidewalls thereof such that a plurality of small gas bubbles exits from the dip tube. The shape of the opening(s) may be varied to suit requirements which might differ with various materials to be used. Alternatively, the bottom portion of the dip tube may be sintered, resulting in a plurality of openings therein of small diameter. It details sealing the lower end of the dip tube and providing one or more small openings therein and/or in the lower portion of the dip tube. The dip tube extends to the bottom of the cylinder and one or more openings are provided in the lower portion of the dip tube.
It is therefore desirable to have alternative designs for the tips of dip tubes for delivery devices that prevent the build-up of reactive products on the inside surface of the dip tube.